FYI, The technology detailed on that page is governed by ITAR for US citizens. You can end up facing some serious penalties if you are a US citizen and build a GPS receiver (capable of operating > 10,000 feet) for someone in another country.
They relaxed the ITAR restrictions on GPS quite a bit a few years ago. The new rules only involve decryption of the precise positioning signals, steerable antennas designed to avoid jamming, and GPS designed as missile guidance technology (ability to deliver 500kg payload at least 300km).
Additionally, the previous restrictions specified they were to be inoperable when BOTH above 18,000m altitude (not 10,000 ft) AND 515 m/s velocity.
Many manufacturers accomplished this by restricting operation when either condition was sensed, but you could find some that could be used in applications that only violated one condition, like high-altitude balloons.
Commercial jetliners never fly at 18,000 m (nor at 515 m/s). Max is about 11,000 m or so, and about 250 m/s. It would be interesting to know if consumer GPS ever worked aboard the Concorde.
You can use offline GPS navigation software on a plane. I did it several times, just as my friends. I use LG G3 and OsmAnd app.
LG G3 has very poor GPS antenna so you have to press the phone against the plane window and wait for 4-5 minutes before it finds sufficient number of sattelites.
If you take pictures from the air with an iPhone, they will be geotagged. When you land and you get internet back, they will be labeled correctly in Photos.app.
Other phones had trouble finding GPS signal in airplanes, but I never had a problem with my iPhone 6s or iPhone 7.
A couple of years back my kid got the GPS working on his Windows phone, using some 3rd party app that cut through all of the other location detection crap. We were able to track our speed and location in a passenger jet flying out of Maui.
> The new rules only involve decryption of the precise positioning signals, steerable antennas designed to avoid jamming, and GPS designed as missile guidance technology (ability to deliver 500kg payload at least 300km).
Now I want to publish all of that info in a book and distribute it world wide, a la PGP Philip Zimmerman style. ITAR...Pssssha!
Somehow the potential repercussions for this feel worse - your information could be used to guide actual missiles against people. I know you can make similar arguments with encryption but at least that can't deliver explosive payloads by itself
